In many indoor environments, it is desirable to detect occupancy or motion. Examples of such systems include motion and/or occupancy sensors used to trigger turning on/off of lights and motion sensors used to implement security systems. Current implementations of monitoring motion or presence of people and pets primarily often rely on a passive infrared (PIR) motion sensors, which detect the heat radiated by living creatures, sometimes combined with an ultrasonic sensor. This often presents a problem of false positive readings due to shortcomings of such sensors (susceptibility to temperature changes, lack of ability to differentiate between pets or people, and dead spots at larger distances). Additionally, these systems are limited to line-of-sight measurements over a relatively small area surrounding the sensor. As such, it is not possible to obtain information about situations in other rooms or locations not in the line-of-sight (such as areas blocked by wall, furniture, plants, etc).